Field of Invention
Various embodiments of the present disclosure relate to a field emission device.
Description of Related Art
As shown in FIG. 1, field emission devices include at least two electrodes and are configured such that a field emission emitter which is provided on a relatively-low-potential electrode (typically, a cathode) of the at least two electrodes.
In a field emission device 100 according to a conventional technique shown in FIG. 1, electrons are emitted from a cathode 110, which has relatively low potential, and attracted to an anode 120.
In field emission devices having a diode structure, the quantity of emitted electrons and acceleration energy of electrons cannot be independently controlled. Therefore, field emission devices generally use a triode structure having an additional gate electrode 130, as shown in FIG. 1.
In the triode field emission device 100, the quantity of electrons emitted from the cathode 110 emitted from the cathode 110 is determined by a potential difference between the gate 130 and the cathode 110 (generally, voltage of the gate 130 in the case where the cathode 110 is grounded). Emitted electrons pass through an opening 131 formed in the gate 130 and are attracted to the anode 120. Acceleration energy of electrons is determined by a potential difference between the anode 120 and the cathode 110.
The field emission device 100 typically uses energy of electrons that are emitted and accelerated. Particularly, in the case of an X-ray source which requires high acceleration energy of electrons, the voltage of the anode 120 is relatively high. In this case, as shown in FIG. 2, an arc discharge may occurs due to dielectric breakdown of the anode electrode 120, the gate electrode 130 or between the anode electrode 120 and the cathode electrode 110. Particularly, if an arc discharge is caused on the gate electrode 130 by high voltage atmosphere of the anode 120, the voltage of a power supply connected to the gate 130 may be instantaneously increased. This induces a strong electric field on the field emission emitter and thus may damage the field emission emitter. In addition, if an arc discharge directly influences the cathode 110, the emitter, etc. which are present on the cathode 110 may be damaged. Given this, it is preferable that the diameter of the opening 131 of the gate 130 is less than double the distance between the gate 130 and the cathode 110.